Frequency translators or phase modulators have many applications in various signal generating and processing areas, such as variable frequency and other types of signal sources. Serrodyne type phase modulators create a phase shift as a function of time to produce a frequency translation in a phase modulator. The phase modulator includes an input frequency, which is acted on by the phase modulator to produce a translated output frequency. The frequency translation is achieved by producing a .phi.t function which causes a frequency translation of .DELTA..omega. in the phase modulator. The function .phi.t requires an ever increasing phase shift. This requirement is not practical in conventional circuitry.
The .phi.t function can be produced if .phi.t is reset after reaching 2.pi.. The frequency phase modulator operates on this principle, creating a magnitude increasing phase change until 2.pi. is reached, resetting to zero (0) and then continuing. For some high resolution applications, i.e. high linearity it is necessary to precisely control the slope of the increasing magnitude waveform. High linearity is difficult to achieve in prior art frequency phase modulators, especially where the time period is relatively long.
The present invention therefore was developed to generate a highly linear controlled slope waveform in a frequency phase modulator, for utilization, for example in high resolution variable frequency sources and fiber optic gyros.